Wave guide magic-tee junctions



July 30, 1957 E. A. N. wHlTl-:HEAD 2,801,391

' WAVE GUIDE MAGIC-TEE JUNCTIONS Filed June 12, 1953 5m V2A/mp;

United States Patent O WAVE GUIDE MAGIC-TEE JUNCTIONS Eric Arthur North Whitehead, St. Albans, England, as-

signor to Elliott Brothers (London) Limited, London, England, a British company Application .lune 12, 1953, Serial No. 361,333

Claims priority, application Great Britain June 13, 1952 8 Claims. (Cl. 333-11) 'I'his invention relates to waveguide junctions, i. e. rigid components formed with a plurality of internal passages each communicating with at least one other such passage and intended to serve for the propagation of electromagnetic waves therethrough, the passages constituting waveguide sectionsand being adapted to be connected, at any end which is open, to an externally arranged waveguide or other component.

A frequent requirement in current radar practice is a waveguide junction having eight open passage ends (an open passage end' being termed an arm) and having the internal passages inter-connecting these arms so arranged that when four of the arms are connected each to a dierent one of four receiving aerials, the amplitudes and phases of the waves incident upon which are represented by the four `couplers designated A, B, C, -D, respectively, the outputs at the four remaining arms will have amplitudes 1/z(A-j-Bj-C|D), 1/2(A+B,-CD), 1/z(A-Bj-C-D) and 1/2(ABC|D), respectively. Such a waveguide junction will be termed herein an eight-arm waveguide junction and this invention is concerned more particularly with improvements in these junctions. j

It has been known for some time that four four-arm waveguide junctions of the hybrid or magic Tee type may be interconnected to produce an eight-arm waveguide junction but other four-arm junctions, such as hybrid rings, have been employed in preference because of the difculty of manufacturing hybrid Tee junctions which are matched and the didiculty of arranging these junctions in a convenient form which will lavoid undue weight and complexity of the interconnecting waveguides.

I have now found that it is possible to produce a highly satisfactory and compact eight-arm waveguide junction by interconnecting four magic Tee waveguide junctions which are not themselves matched and that the resulting junction has considerable advantages over those produced from four-arm junctions of other types since the symmetry of the magic Tee junction guarantees the accuracy of the signal additions and subtractions which it is called upon to perform.

Accordingly, this invention consists in an veight-arm waveguide junction composed of four unmatched magic Tee junctions arranged symmetrically with the longitudinal axes of their straight-through passages parallel to each other and the centre points of these axes located at the four corners of a rectangle, the shunt' arms ot the magic Tee junctions being connected to each other in pairs and the series arms of these junctions being also connected to each other in pairs, and matching devices located in the interconnected shunt arms and in the interconnected series arms either midway between the junctions of the respective pairs of magic Tee junctions or symmetrically one at either side of the corresponding midway point.

In order that the invention may be clearly understood, one form thereof will now be described by Way of ex- Patented July 30, 1957 ample with reference to the accompanying drawing which is a perspective view of an eight-arm waveguide junction.

The eight-arm waveguide junction illustrated comprises four unmatched magic Tee junctions indicated generally .at 1, 2, 3 and 4 respectively arranged symmetrically with the longitudinal axes of their straight-through passages (each indicated by the reference 5) parallel to each other and the centre points of these axes located at the four corners of a rectangle. The shunt arms of the magic Tee junctions 1, 2, 3 and 4 are connected to each other to provide the two arms 7 interconnecting the junctions 1 and 2 and the junctions 3 and 4 respectively and the series arms of these junctions are also connected to each other in pairs to provide the two arms 6 interconnecting the junctions 1 and 4 and the junctions 2 and 3 respectively. A matching device 8 is located midway along the length of each of the arms 6 in one of the planes of symmetry of the combination of four-arm junctions 1, 2, 3 and 4. Two further matching devices 8 comprising a pair are located in each of the arms 7 of the combination, the component parts of each pair of devices 8 being symmetrically disposed with respect to the corresponding plane of symmetry of the combination of junctions. The matching devices 8 are preferably inductive or capacitive shunt elements, such as irises.

It will be appreciated that each pair of matching devices 8 located in the arms 7 may be replaced by a single matching device 8 located midway along the length of each arm 7 between the hybrid magic Tee junctions 1 and 2, and 3 and 4 respectively. Furthermore the single matching device 8 located in each arm 6 may be replaced by a pair of such devices so long as the cornponent parts of the pair are symmetrically disposed with respect to the corresponding plane of symmetry. The eight-arm junction obtained may readily be matched accurately by appropriate adjustment of the matching devices 8 referred to, the matching devices 8 on opposing sides of the rectangular arrangement being identical by reason of the symmetry of the latter. It should be noted that the employment of pairs of matching devices 8 in each side of the rectangular arrangement makes possible a better match over a wide band of frequencies.

It will be understood that the lengths of the waveguides coupling the individual hybrid Tee junctions together are such that correct phasing of the various signals is obtained.

In the operation of the eight-arm waveguide junction described the output signals from four different receiving aerials are respectively fed into the open ends of two straight-through passages 5 the centre points of the axes of which passages are located at diagonally opposed corners of the rectangle on which are located the centre points of the axes of the four passages 5. Thus, for example, the four signals are respectively fed into the open ends of the passages 5 of the magic Tee junctions 2 and 4. Assuming that the amplitudes and phases of these signals are represented by the coupler numbers A, B, C and -D and that A and B are respectively fed into the ends of the passage 5 of the junction 4 and C and -D are respectively fed into the ends of the passage 5 of the junction 2 then the signal travelling along the series arm 6 of the junctions 1 and 4 towards the passage 5 of the junction 1 is (A-B); the signal travelling along the shunt arm 7 of the junctions 3 and 4 towards the passage 5 of the junction 3 is (A+B); the signal travelling along the series arm 6 of the junctions 2 and 3 towards the passage 5 of the junction 3 is (C-j-D); and the signal travelling along the shunt arm 7 of the junctions 1 and 2 towards the junction 1 is (C-D). This results in an output signal of 1/2(A-B-C}D) at one end of the passage 5 of the junction 1 and an output signal of 1/2(A-B+CD) at 3 the other endv thereof and also in an output signal of 1/2(A-|.B'-C-D) at one end of the passage 5 of the junction 3 and an output signal of 1/2(A{Bj-C|D) at the other en d thereof. l

What I claim is:

1. An eight-arm waveguide junction composed of four unmatched magic Tee junctions Veach having a straightthrough open-ended passage, a shunt arm and a series arm,` said junctions being arranged symmetrically wigh the longitudinal axes of their straight-through passages parallel to each other and the centre points of these axes located at the four corners of a rectangle, the shunt arms of the magic Tee junctions being connected to each other in pairs and the series arms of these. junctions being also connected to each other in pairs, and a matching: device. located in each pair of interconnected shunt and series. arms midway between the J'Untions of the respective pairs of magic Teev junctions.

2. An eight-arm waveguide junction composed of tourv unmatched magic Tee junctions each having a straightthrough open-ended passage, a shunt arm and a series arm, said junctions being arranged symmetrically with the longitudinal aXes of their straight-through passages parallel to each other and the centre points of these axes located at the four corners of a rectangle, the shunt arms of the magic Tee junctions being Connected to each other in pairs and the series arms of these junctions being also Connected t .each other in pairs, and at least one matching device located in each pair of interconnected shunt and series arms and disposed symmetrically with respect to the midway point of each such pair of interconnected arms,

3. An eight-arm waveguide junction composed of four unmatched magic Tee junctions each having a straightthrough open-ended passage, a shunt arm andV a series arm, said junctions being arranged symmetrically with the longitudinal axes of their straight-through passages parallelV to each other and the centre points of these axes located at the four corners of a rectangle, the shunt armsof the magic Tee junctions being connected' toeachother in pairs and the series arms of these junctions being also connected to each other in pairs, and a pair of matching devices located in each pair of interconnected shunt and series arms and disposed symmetrically one oneitherside of theV corresponding midway point between tbe respective pairs of magic Tee junctions.

4. An eightarm waveguide junction composed o f four unmatched magic Tee junctions each composed of an open-ended waveguide of constant rectangular cross-section throughout its length to provide a straight-through uninterrupted passage, one cross-sectional dimension of said` passage being larger than the other, a shunt arm ofl the same rectangular cross-section opening at one end into the open-ended waveguide through one of the smaller dimensioned walls of the latter substantially midway along its length and a series arm of the sameV rectangular cross-section opening at one end into the openended waveguide through one of the larger dimensioned walls of the latter substantially midway along its length, said junctions being arranged symmetrically with the longitudinal axes of their straight-through passages parallel with each other and the centre points of these axes located at the four corners of a rectangle, the shunt arms of the magic rFee junctions being connected to each other in pairs and the seriesV arms of these junctions being also connectedV to each other in pairs, and a matching device located in each pair of interconnected shunt and series arms.

5. An eight-arm waveguide junction composed of four unmatched magic Tee junctions each composed of an open-ended waveguide of constant rectangular cross-sec tion throughout its length to provide a straight-through uninterrupted passage, one cross-sectional dimension of said passage being larger thanthe other,y a shunt arm of the same rectangular cross-section opening at one end into the open-ended waveguide through one of the smaller dimensioned walls of the latter substantially midway along its length and a series arm of the same rectangular crosssection opening at one end into the open-ended waveguide through one of the larger dimensioned walls of the latter substantially midway along its length, said junctions being Y arranged symmetrically with the longitudinal axes of their straight-through passages parallel with each other and the centre points of these axes located at the four corners of a rectangle, the shunt arms of the magic Tee junctions being connected to each other in pairs and the series arms of these junctions being also connected to each other in pairs, and a matching device located in each pair of interconnected shunt and series arms and extending across these transversely to their direction of length.

6. An eight-arm waveguide junction composed of four unmatched magic Tee junctions each composed of an openended waveguide ofconstant rectangular cross-section throughout its length to provide a straight-through uninterrupted passage, one cross-sectional dimension of said passage being 'larger than the other, a shunt arm of the same rectangularV cross-section opening at one end into the open-ended waveguide through one of the smaller dimensioned wallsof the latter substantially midway along its length and a series arm of the same rectangular crosssection opening at one end into tbe open-ended waveguidethrough one of the larger dimensioned wallsof the latter substantially midway along its length, said junctions being arranged symmetrically with the longitudinal axes of their straight-through passages parallel with each other `and the centre points of these axes located at the four corners of a rectangle, the shunt arms of the magic Tee junctions being connected to each other in pairs and the series arms of these junctions being also connected to each otberein pairs, and at least one matching device located in each pair of interconnected shunt and series arms and disposed symmetrically with respect to the midpoint of each such pair of interconnected arms.

7. An eight-arm waveguide junction composed of four unmatched magic Tee junctions each composed of an openended waveguide of constant rectangular cross-section throughout its` length to provide a straight through uninterrupted passage, one cross-sectional dimension of said passage being larger than the other, a shunt arm of the same rectangular cross-section opening at one end into the open-ended waveguide through one of the smaller dimensioned walls of the latter substantially midway along its length and' a series arm of the same rectangular cross section; opening at one end into thel open-ended waveguide through onel of the larger dimensioned walls of the latter substantially midway along its length, said junctions being arranged symmetrically with the longitudinal axes of their straight-through passages parallel with each other and the centre points of theseaxes` located at the four corners of a rectangle, the shunt arms of the magic Tee junctions being connected to each other in pairs, and the series arms of these junctions being also connected to each other in pairs, and a pair of matching devices located in each pair of interconnected shunt and series arms and disposed symmetrically one on either side of the corresponding midway point between the respective pairs of magic Tee junctions.

8. An eight-arm waveguide junction composed of four unmatched magic 'Fee junctions each composed of an openended waveguide of' constant rectangular cross-,section throughout Aits length to provide a straight-through uninterrupted` passage, one cross-sectional dimension of said j passage being larger than the other, a shunt arm of the same`rectangular cross-section opening at one end into the open-endedA waveguide through one of the smaller dimensioned walls of the latter substantially midway along its length and a series arm of the same rectangular cross'- section opening at one end into the open-ended waveguide through 'one of the larger dimensionedr walls of the latter substantially midway along its length, said junctions being arranged symmetrically with the longitudinal axes of their straight-through passages parallel with each other and the centre points of these axes located at the four comers of a rectangle, the shunt arms of the magic Tee junctions being connected to each other in pairs, and the series arms of these junctions being also connected to each other in pairs, a pair of matching devices located in each pair of interconnected shunt arms and symmetrically disposed one on either side of the midway point of these interconnected shunt arms and a matching device located in each References Cited in the le of this patent UNITED STATES PATENTS Lewis May 6, 1952 Beck Oct. 12, 1954 

